Format Cube View based on third Header Override expansion

I am using header overrides on my columns to create three column expansion levels.

I need to add conditional formatting based upon the header display text of "HPU" in this third expansion so that only sections with "HPU" in the header are set to three decimal places. 

I do not want to build every HPU column separate from the others, as this would require the build of 108 columns, instead of 12 columns.

The system will not let me call that third expansion level in my conditional formula.

Any help would be greatly appreciated!